Coated articles are known in the art for use in window applications such as insulating glass (IG) window units, vehicle windows, monolithic windows, and/or the like. In certain example instances, designers of coated articles often strive for a combination of high visible transmission, desired color, low emissivity (or emittance), low sheet resistance (RS), low U-values in the context of IG window units, and/or low specific resistivity. Desired visible transmission and color may permit coated articles to be used in applications where these characteristics are desired such as in architectural or vehicle window applications, whereas low-emissivity (low-E), low sheet resistance, and low specific resistivity characteristics permit such coated articles to block significant amounts of infrared (IR) radiation so as to reduce for example undesirable heating of vehicle or building interiors.
Thus, it will be appreciated that low emittance values, low sheet resistance (RS) and low specific resistivity are desirable features in many situations. For coated articles having a coating including an IR reflecting layer(s) of Ag or the like, it is the IR reflecting layer(s) that primarily determines the emittance, sheet resistance, and specific resistivity (or resistance) values of the coated article. It is noted that specific resistivity (or resistance) of a particular layer or coating is RS multiplied by thickness of the IR reflecting layer(s). Specific resistance/resistivity (SR) is thus a good indicator of the quality of an IR reflecting layer; in particular, a better more conductive IR reflecting layer (e.g., silver based layer) has a lower specific resistance.
Consider a typical coated article with the following layer stack. This coated article is suitable for use in an IG (insulation glass) window unit. For the coated article listed below, the coating includes layers that are listed from the glass substrate outwardly.
LayerThickness ({acute over (Å)})GlassTiOx140 {acute over (Å)}SnOx100 ÅZnAlOx 70 {acute over (Å)}Ag118 {acute over (Å)}NiCrOx 20 {acute over (Å)}SnOx223 ÅSiNx160 {acute over (Å)}
As is typically the case, the silver (Ag) layer was formed by sputtering a planar silver target in an atmosphere including only argon (Ar) gas. The silver (Ag) layer of the above coated article has a thickness of 118 angstroms (Å) and a sheet resistance (RS) of 4.6 ohms/square. This translates into a specific resistivity (RS multiplied by thickness of the IR reflecting layer) for the silver IR reflecting layer of 5.43 micro-ohms.cm.
While the aforesaid specific resistivity (SR) of the silver IR reflecting layer is adequate in many situations, it would be desirable to improve upon the same. For example, if the specific resistivity (SR) of the silver layer could be lowered, then the coating could realize improved thermal properties (e.g., lower U-value, lower emittance, and/or the like) given an IR reflecting layer of the same thickness. Thus, a lower specific resistance of the IR reflecting layer(s), and thus a lower RS and emittance/emissivity are desirable, as they permits thermal properties of the coating to be improved.
In view of the above, it will be appreciated that reduced emittance, reduced sheet resistance, and reduced specific resistance are often desired properties in certain coated articles. Certain example embodiments of this invention seek to provide a method and/or system for making coated articles which permits the coated articles to have reduced emittance and/or resistance values.
In certain example embodiments of this invention, it has surprisingly been found that the use of krypton (Kr) gas in the sputter chamber when sputter-depositing an IR reflecting layer of or including silver unexpectedly improves the quality of the IR reflecting layer thereby permitting the coated article to realize improved thermal properties with a given thickness of the IR reflecting layer.
In particular, in certain example embodiments of this invention, it has been found that the use of at least Kr gas in the sputtering process of the IR reflecting layer unexpectedly results in an IR reflecting layer with a lower specific resistivity (SR). The lower the SR of an IR reflecting layer, the lower the emittance of the coated article with an IR reflecting layer of a given thickness. Likewise, the lower the SR of an IR reflecting layer, the lower the U-value of an IG unit including a similar coating having an IR reflecting layer of a given thickness. Thus, lowering the SR of an IR reflecting layer permits thermal properties of a coated article to be improved given an IR reflecting layer(s) of like thickness. Alternatively, lowering the SR of an IR reflecting layer permits thermal properties of a coated article to remain substantially the same while reducing the thickness of the IR reflecting layer(s) which may be desirable for increasing visible transmission or the like in certain situations.
Thus, it can be seen that lowering the SR of an IR reflecting layer is advantageous. As discussed herein, it has been found that the use of at least Kr gas in the sputtering process for the IR reflecting layer(s) surprisingly results in an IR reflecting layer(s) with a lower SR.
In certain example embodiments of this invention, there is provided a method of making a coated article for use in a window unit, the method comprising: providing a glass substrate for supporting a multi-layer coating; and depositing an infrared (IR) reflecting layer comprising silver on the glass substrate, wherein said depositing of the IR reflecting layer comprises sputtering at least one target comprising silver that is located in a chamber; providing at least krypton gas in the chamber during said sputtering of the target comprising silver.
In other example embodiments of this invention, there is provided a method of making a coated article including a layer comprising silver, the method comprising: sputtering at least one target comprising silver that is located in a chamber; and providing at least krypton gas in the chamber during said sputtering of the target comprising silver.
In still further example embodiments of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: at least one infrared (IR) reflecting layer comprising silver located between at least first and second dielectric layers; and wherein the IR reflecting layer further comprises krypton.